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serial: fix off by one errors

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In zs_console_putchar() occurs:

	if (zs_transmit_drain(zport, irq))
		write_zsdata(zport, ch);

However if in zs_transmit_drain() no empty Tx Buffer occurs, limit reaches
-1 => true, and the write still occurs.

This patch changes postfix to prefix decrements in this and similar
functions to prevent similar mistakes in the future.  This decreases the
iterations with one but the chosen loop count was arbitrary anyway.

In sunhv limit reaches -1, not 0, so the test is off by one.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roel Kluin 2009-06-22 18:41:56 +01:00 committed by Linus Torvalds
parent 607c268ef9
commit 52e3632ea6
3 changed files with 7 additions and 7 deletions
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6
drivers/serial/sb1250-duart.c
View file

@ -204,7 +204,7 @@ static int sbd_receive_drain(struct sbd_port *sport)
{
int loops = 10000;
while (sbd_receive_ready(sport) && loops--)
while (sbd_receive_ready(sport) && --loops)
read_sbdchn(sport, R_DUART_RX_HOLD);
return loops;
}
@ -218,7 +218,7 @@ static int __maybe_unused sbd_transmit_drain(struct sbd_port *sport)
{
int loops = 10000;
while (!sbd_transmit_ready(sport) && loops--)
while (!sbd_transmit_ready(sport) && --loops)
udelay(2);
return loops;
}
@ -232,7 +232,7 @@ static int sbd_line_drain(struct sbd_port *sport)
{
int loops = 10000;
while (!sbd_transmit_empty(sport) && loops--)
while (!sbd_transmit_empty(sport) && --loops)
udelay(2);
return loops;
}

2
drivers/serial/sunhv.c
View file

@ -461,7 +461,7 @@ static void sunhv_console_write_paged(struct console *con, const char *s, unsign
break;
udelay(1);
}
if (limit <= 0)
if (limit < 0)
break;
page_bytes -= written;
ra += written;

6
drivers/serial/zs.c
View file

@ -231,7 +231,7 @@ static int zs_receive_drain(struct zs_port *zport)
{
int loops = 10000;
while ((read_zsreg(zport, R0) & Rx_CH_AV) && loops--)
while ((read_zsreg(zport, R0) & Rx_CH_AV) && --loops)
read_zsdata(zport);
return loops;
}
@ -241,7 +241,7 @@ static int zs_transmit_drain(struct zs_port *zport, int irq)
struct zs_scc *scc = zport->scc;
int loops = 10000;
while (!(read_zsreg(zport, R0) & Tx_BUF_EMP) && loops--) {
while (!(read_zsreg(zport, R0) & Tx_BUF_EMP) && --loops) {
zs_spin_unlock_cond_irq(&scc->zlock, irq);
udelay(2);
zs_spin_lock_cond_irq(&scc->zlock, irq);
@ -254,7 +254,7 @@ static int zs_line_drain(struct zs_port *zport, int irq)
struct zs_scc *scc = zport->scc;
int loops = 10000;
while (!(read_zsreg(zport, R1) & ALL_SNT) && loops--) {
while (!(read_zsreg(zport, R1) & ALL_SNT) && --loops) {
zs_spin_unlock_cond_irq(&scc->zlock, irq);
udelay(2);
zs_spin_lock_cond_irq(&scc->zlock, irq);